6063 aluminum alloy profiles are widely used for their good plasticity, moderate heat treatment strength, good welding performance and gorgeous color on the surface after anodizing. However, there are often some defects in the production process such as:
1 stroke, rub, bruise
Scratches, abrasions, and bruises are surface damage caused when a profile flows out of a die hole and contacts a tool, equipment, or the like in a subsequent process.
1.1 main reason
1 The surface of the ingot is attached with impurities or segregation of the ingot composition. When there is a large amount of segregation floating on the surface of the ingot and the ingot is not homogenized or the effect of homogenization is not good, there is a certain amount of hard metal particles in the ingot, and the metal flows through the working belt during the extrusion process. These segregation floats or hard metal particles adhere to the surface of the work belt or cause damage to the work belt, eventually causing scratches on the surface of the profile;
2 There is debris in the mold cavity or working belt, and the hardness of the working belt of the mold is low, so that the surface of the working belt is injured during the extrusion and the profile is scratched;
3 There are bare metal or graphite strips on the discharge track or pendulum bed with hard inclusions, which cause scratches on the surface of the profile when it comes into contact with the profile;
4 When the fork rod is sent from the discharge rail to the swinging bed, the profile is scratched due to the excessive speed;
5 caused a scratch on the bed by artificially dragging the profile;
6 During the transportation process, the profiles are rubbed or squeezed together to cause damage.
1.2 Solution
1 Strengthen the control of the quality of the ingot;
2 Improve the quality of the mold, the mold is periodically nitrided and the nitriding process is strictly performed;
3 Separate the profile from the auxiliary tool with soft felt to minimize contact damage between the profile and the accessory;
4 Handle with care, try to avoid dragging or flipping the profiles at will;
5 Reasonably place the profiles in the material frame to avoid rubbing each other.
2 mechanical performance is unqualified
2.1 main reasons
1 When the temperature is too low during extrusion, the extrusion speed is too slow, and the outlet temperature of the profile at the outlet of the extruder does not reach the solid solution temperature, and the solid solution strengthening effect is not obtained;
2 There are few fans at the exit of the profile, and the air volume is not enough, resulting in a slow cooling rate. The profile cannot be lowered to below 200 °C in the shortest time, so that the coarse Mg2Si precipitates prematurely, which reduces the solid solution phase and affects the heat treatment of the profile. Mechanical behavior;
3 The composition of the ingot is unqualified, and the content of Mg and Si in the ingot does not meet the standard requirements;
4 The ingot is not homogenized, so that the Mg2Si phase precipitated in the ingot structure cannot be re-dissolved in a short time of extrusion, resulting in insufficient solid solution and affecting product performance;
5 aging process is not good, hot air circulation is not smooth or thermocouple installation position is not correct, resulting in insufficient aging or overaging.
2.2 Solution
1 Reasonably control the extrusion temperature and extrusion speed to keep the profile at the outlet temperature of the extruder above the minimum solution temperature;
2 to strengthen the air-cooled conditions, the conditional factory can install the atomization cooling device, in order to meet the minimum requirements of the 6063 alloy cooling gradient;
3 Strengthen the quality management of ingots;
4 homogenizing the ingot;
5 Reasonably determine the aging process, correctly install the thermocouple, and correctly place the profile to ensure smooth circulation of the hot air.
3 geometric size is out of tolerance
3.1 main reasons
1 Due to unreasonable mold design or manufacturing error, improper extrusion process, misalignment of the mold and the extrusion tube, unreasonable lubrication, etc., the flow velocity of each point in the metal flow is too large, resulting in internal stress causing deformation of the profile;
2 Due to excessive traction or excessive amount of stretch straightening, the profile size is too poor.
3.2 solution
1 Reasonable design of the mold to ensure the accuracy of the mold;
2 Correctly execute the extrusion process and set the extrusion temperature and extrusion speed reasonably;
3 to ensure the alignment of the equipment;
4 Use moderate traction to strictly control the amount of stretch straightening of the profile.
4 squeeze ripple
Extrusion corrugation refers to the situation similar to water ripple on the surface of extruded profiles, generally without hand feeling, and it is obvious under the action of light.
4.1 main reasons
1 The traction machine periodically pulsates up and down to partially bend the surface of the profile;
2 The mold design is unreasonable, and the working belt vibrates under the action of the pressing force, causing the profile to corrug.
4.2 Solution
1 to ensure that the tractor runs smoothly;
2 Reasonable design of the mold structure.
5 pockmark
The pockmark refers to the density of the surface on the surface of the profile, with a trailing, very fine nodules, a distinct hand and a sharp sensation.
5.1 main reasons
Due to the inclusions in the ingot or the metal or debris adhering to the working belt of the mold, the aluminum is clamped off by the high-temperature and high-pressure aluminum during the extrusion, and the surface of the profile is formed on the surface of the profile.
5.2 Solution
1 Properly reduce the extrusion speed, using a reasonable extrusion temperature and mold temperature;
2 Strictly control the quality of the ingot, reduce the inclusion content in the ingot, and homogenize the ingot;
3 Strengthen the quality management of mold repair.
6 dark spots
After the anodizing of the profile, a nearly circular black-gray spot appears locally, and the profile is distributed equidistantly on the surface of the longitudinally placed bed of the profile, and the size is different.
6.1 main reason
Due to insufficient air cooling at the exit of the extruder, the aluminum material contacts the pendulum bed at a higher temperature, and the cooling rate of the contact portion is different at other positions, and a coarse Mg2Si phase is precipitated, and the portion becomes black after the anodizing treatment. gray.
6.2 Solution
1Strengthen the air-cooling strength, avoid the spacing of the profile on the bed to be too small, and ensure the temperature gradient of air cooling;
2 Conditional factories should use a combination of atomized water cooling and air cooling to completely eliminate dark spots.
7 stripes
There are many types of stripe defects in extruded profiles, and the formation factors are also complicated. Here, only the causes and solutions of some common strips are discussed.
7.1 friction pattern
Each time the mold is squeezed on the optical mold, the lines cannot correspond one-to-one, light and heavy.
7.1.1 Main reasons
During the extrusion process, the profile exits the die orifice momentarily against the work belt, forming a pair of dry friction pairs in the hot state, and dividing the work zone into two zones - the adhesion zone and the sliding zone. In the adhesion zone, the metal dots are subjected to forces from at least two aspects: friction and shear. When the frictional force of the metal dots in the adhesion zone is greater than the shearing force, the metal dots adhere to the surface of the working zone of the adhesive zone, and the surface of the profile is scratched to form a rubbing pattern.
7.1.2 Solution
1Adjust the exit angle α of the working belt of the mold so as to be in the range of -1° to -3°, which can reduce the height of the adhesive zone of the working belt, reduce the friction of the zone, and increase the sliding zone;
2 Efficient mold nitriding treatment to maintain the surface hardness of the mold above HV900; the surface of the working belt can reduce the friction of the adhesive area and reduce the friction pattern.
7.2 organization stripes
7.2.1 Main reasons
The ingot casting structure is uneven, the composition is segregated, there are serious defects under the epidermis of the ingot, the uniformity of the ingot is not adequately treated, and the surface composition of the profile is not uniform during the subsequent extrusion process, so that the profile is oxidized. The coloring ability is different, forming tissue streaks.
7.2.2 Solution
1 Reasonably execute the casting process to eliminate or reduce tissue segregation;
2 ingot surface wagon;
3 Carefully carry out the ingot homogenization treatment.
7.3 metallic bright lines
It is bright in the oxidized white material, and in most cases is straight and has a variable width. In the oxidative coloring material, the stripes are lightly colored.
7.3.1 Main reasons
When the metal flow is rubbed or the deformation is extremely severe, the local temperature of the metal will rise very high, and the uneven metal flow will also cause the crystal grains to be severely broken, and then recrystallization will occur, causing the structure to change, and subsequent oxidation treatment. The result is a vertical bright streak on the surface of the profile, which causes the profile to be colored or light-colored.
7.3.2 Solution
1 Reasonable design of the mold structure;
2 mold processing should pay attention to the transition of the working belt to prevent the work belt drop;
3 to ensure that the mold bridge is in the shape of a drop, eliminating the edges and corners.
7.4 welded stripe
The weld stripe, also known as the weld seam, is straight and long, and is mostly light gray in the oxidized white material, and has a light color in the coloring material.
7.4.1 Main reasons
1 mold split hole design is too small;
2 The depth of the welding chamber is not enough to ensure sufficient pressure;
3 Insufficient supply of aluminum in the mold welding chamber during extrusion;
4 The extrusion process is unreasonable and the lubrication is improper.
7.4.2 Solution
1 Reasonable design of the mold structure;
2 pay attention to the coordination of extrusion temperature and extrusion speed;
3 Minimize lubrication or no lubrication.
8 crack
The transverse tearing of the metal when the profile is subjected to tensile stress and the degree of surface formation is different.
8.1 main reason
1 due to the frictional force, the metal surface layer is subjected to additional tensile stress, and when the additional tensile stress is greater than the surface metal tensile strength, cracks are generated;
2 Extrusion temperature is too high, the tensile strength of the metal surface decreases, and cracks are generated under the action of friction;
3 When the extrusion speed is too fast, the additional tensile stress on the metal surface layer causes the profile to crack.
8.2 Solution
Squeeze process parameters are strictly controlled to ensure reasonable exit speed and outlet temperature.
9 waves, twists, bends
Waves, twists, and bends are profile defects due to uneven metal flow.
9.1 main reason
1 The mold working belt is not designed reasonably, resulting in uneven metal flow;
2 The extrusion speed is too fast or the extrusion temperature is too high, resulting in uneven metal flow;
3 mold hole layout is unreasonable, resulting in uneven metal flow;
4 guides are not suitable or no guides are installed;
5 lubrication is not suitable.
9.2 Solution
1 trimming the working belt of the mold to make the metal flow evenly;
2 using a reasonable extrusion process, under the premise of ensuring the outlet temperature, try to use low temperature extrusion;
3 reasonable design of the mold structure;
4 configure a suitable guide;
5 reasonable lubrication;
6 traction with a tractor.
10 bubbles
The surface layer metal of the profile and the base metal are locally continuous or intermittently separated, and appear as circular or partially continuous protrusions.
10.1 main reason
1Because the size of the extrusion tube is too long after long-term use, the gas in the cylinder is not removed during extrusion, and the surface of the deformed metal flows out along the elastic region of the front end to cause bubbles;
2 There are grooves on the surface of the ingot or there are pores in the ingot structure. The ingot is filled with gas when the pier is thick, and the gas enters the metal surface layer when squeezed;
3 When extruding, the ingot or mold is filled with moisture and oil. Since water and oil are volatilized into gas by heat, they are drawn into the surface of the profile to form a gas in the high-temperature and high-pressure metal flow;
4 equipment exhaust device is not working properly;
5 metal filling is too fast, resulting in poor extrusion and exhaust.
10.2 Solution
1 Reasonable selection and equipped with extrusion tools, timely inspection and replacement;
2 Strengthen the quality management of the ingot and strictly control the surface quality and gas content of the ingot;
3 to ensure that the exhaust system of the equipment works normally;
4 Scissors, extrusion tubes and molds should be as little or no oil as possible;
5 Reasonably control the extrusion speed and exhaust as required.
11 graphite pressed
The shallow superficial layer along the longitudinal direction of the profile is a strip of semi-exposed pores, a few millimeters short and a few centimeters or more. The main component in the pores is graphite.
11.1 main reason
1 due to the high proportion of graphite in the graphite lubricant or the graphite is not completely stirred uniformly, there are particles or massive graphite;
2 The graphite lubricant is applied too close to the split or the hole. When the graphite is pressed, the graphite does not enter the pressure, but is impregnated into the superficial layer of the product by the high temperature and high pressure metal flow to form graphite.
11.2 Solution
1 use high quality lubricants;
2 Lubricant should be applied away from the split hole or the hole, and use little or no lubricant.
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